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First PhD defended!

Zhaoen Su (PhD 2017) is the first member of our group. Literally, he started in the summer of 2012 before I arrived to Pittsburgh. Together with others from the first cohort he built our research program from scratch – an empty room for a lab, and no cleanroom process for device fabrication.

Zhaoen first focused on Ge/Si nanowire devices. Through hard work he made great progress and achieved supercurrents and tunable double quantum dots. Facing an uphill battle with charge instabilities, he decided to transpose his project to InSb wires. He got excited about quantum dots coupled to superconducting contacts and realized Andreev molecules, which we have already written up. As Zhaoen begins his new position in the Bay Area, there are still 2 exciting experiments that he has performed waiting to be published.

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You can see him holding a mini Cathedral of Learning in the gif above. Congratulations, Zhaoen, and good luck in Silicon Valley!

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Quantum Computing for Nerds From Other Fields

Here are videos from the Quantum Computing Session at the Frontiers of Science Symposium organized by NAS last year. This event brings together young researchers from all fields of study to explain to each other what they are working on. So, if you are a quantum physicist, you will not learn from these videos. If you are my grandmother, same – unless you are my grandmother with a PhD. If you are a biologist, an astrophysicist or a historian – these vidoes may be interesting for you.

Quantum Computing – Krysta Svore, Microsoft Research from Kavli Frontiers of Science on Vimeo.

Quantum Computing – Sergey Frolov, University of Pittsburgh from Kavli Frontiers of Science on Vimeo.

Quantum Computing – Aram W. Harrow, Massachusetts Institute of Technology from Kavli Frontiers of Science on Vimeo.

Thanks to Emanuel Gull and Daniela Oliveira for organizing the session.

Postdoc positions available in Frolov lab

Postdoctoral position in experiment quantum nanoscience is available at Frolov lab at the University of Pittsburgh. Research topics include but are not limited to non-Abelian statistics and topological qubits with Majorana fermions; interacting topological phases and work towards the discovery of parafermions; quantum simulation with semiconductor nanostructures such as quantum dots in nanowires. Typical projects involve a collaboration with a graduate student, extensive use of on-campus facilities at Petersen Institute for Nanoscience and Engineering, and low temperature transport measurements in dilution refrigerators. Interested candidates should email their CV and describe their interests in an email to frolovsm@pitt.edu.

https://frolovlab.org/

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Group bonding

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New Trends in Trending

Today Nature Publishing House has announced the creation of a new and long overdue journal dedicated to publishing the ‘most hottest’ high impact research. The new magazine, called ‘New Trends in Trending’ is dedicated to publishing results that would not have been otherwise published in any other journal for at least five years into the future. Alongside this so-called ‘hyper-original research’, the new monthly will feature a horoscope, and comes with a lottery to win an Island off the coast of Kamchatka.

“Our aim is the impact factor of 1000” wrote Chief Editor Dr. Quickley R. Lookthrough in his first editorial “and our market study tells us this is how we get there”.

Manuscript submission guidelines require that along with the scientific title of each submitted manscript, the authors provide a ‘clickbait’ version of the title ‘to facilitate the broadest dissemination of to the most general audience possible’. A ‘clickbait’ title is meant to convey the premise of the work, but leave the conclusion concealed such that the reader is encouraged to click on the link to find out more. In order to assist the authors, the following clickbait title examples are provided:

They were measuring a graphene device, and then THIS happened!

Thirty-two line plots with error bars that will blow your mind. (You won’t believe the number seventeen!)

Two electrons did whaaat?

If you are doing science and you are older than 3 and younger than 98 you are in for a big surprise

Jaw-dropping discovery hits the field of dissipative porous multiphase systems like a hurricane

These quantum systems thought nobody was watching…

Why this new scaling theory is breaking the internet

Experimentalists feel stupid for not doing these measurements

Don’t read this if you DO NOT want a Nobel Prize

Group website

Sometime during the first year of our group I asked one of my graduate students to put together a group website. “Let’s first finish our first paper” he replied. This attitude shows how seriously we take websites. Not just anything deserves to have a website. Only things of staggering beautymind-blowing webdesign or the friendliest user interface can be websites. Still,

https://frolovlab.org/

Now that our group has fired out the first series of papers, and even though the papers are still painfully making their way through the antiquated journal system, it is time to unveil a modest yet informative little website.

As a side effect, since this blog no longer represents our whole group my hands are now officially untied, and I can proclaim the most ridiculous thoughts here.

First paper finished

High critical magnetic field superconducting contacts to Ge/Si core/shell nanowires

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My group has crossed an important milestone today – we have finalized and uploaded to arxiv our first publication. We are working on several of them simultaneously, and by the luck of the draw the first one out is a paper in which we share our experience making a particular type of nanowire superconducting.

The one and only good thing about writing papers is that it stimulates the authors to think about the experiment they have done in a special way: to find explanations for strange values and effects that only come forward when you give it that extra careful look. That tenth reading that you do under duress of scientific correctness. When we transition into the era of open science, we will share all our results on the fly, and look like fools for all our misconceptions and mistakes, but we will correct each other and move forward much faster. We will parallelize our intellects to think about each other’s work and won’t need to read the same text over and over again not to miss an embarassing mistake.

For now we just keep writing papers.

Excellent tutorial on one-dimensional systems

Should arxiv have ranking and annotation features?

Arxiv.org is a great resource where many, if not the majority, of results in my field appear long before formal publication in journals. In fact, I don’t have a habit of reading physics journals anymore, but I daily look through new postings on arxiv.I also have two papers submitted only to arxiv, and not to any old-fashioned journal.

That said, arxiv is stuck in the 1990’ies with its focus on lists, TeX, its awkward search and lack of any social network functions. Since it is such a convergence point for the physics community, its backwardness has grown into a serious limiting factor for the free and open scientific process. In other words, what it offers – namely instant publication – is better than what journals offer, but this has in the meantime become the new normal. While what it does not offer is holding us back.

This can be seen in the new massive survey that arxiv has conducted of its own users. In a long list of boring questions about tiny incremental improvements to the website, there is a very important category they called ‘New Services’. You will see that over 55% of survey respondents say that ranking and comment functions, familiar from social networks, reddits, and just, ahem, the entire internet, are either ‘Very Important’ or ‘Somewhat Important’. A smaller majority has just taken the UK out of the EU!

Yet the arxiv program director at Cornell Oya Rieger writes about it as an even split between those who are strongly for these features (~35%) and those strongly against (~35%). She goes on an on about caution and caveats, which basically means that her and the arxiv team are not going to do this on their own. She does mention that the support for these features is stronger among younger users, so there may be a generational divide at play here, and the arxiv team is on the wrong side of this divide from the historical point of view.

Think about it: all of arxiv content is open to the entire internet. If somebody makes a different website which implements these annotation, ranking, search, communication features nicely, and if the community starts using that service, then not having these features as part of arxiv.org itself will be akin to hiding one’s head in the sand – ignoring the new norm that just grew around you. Now, this has not happened yet, but the demand for it is clearly present, as the survey results demonstrate. When this finally happens, it will be the beginning of the end of arxiv, as at that point it will be easier to submit your work to the new website where it can be instantly evaluated, discussed, ranked, categorized and improved through community interactions.

Nanolithography Expert Position

University of Pittsburgh Peteresen Institute of Nanoscience and Engineering is hiring a PhD-level expert in electron beam and optical lithography. This job is for someone to develop lithography processes in close cooperation with research groups at Pitt, and to take full advantage of the Raith e-Line system, as well as of the  brand new Elionix 100kV machine that is shortly arriving to the Carnegie Mellon cleanroom next doors. Our nano team, once complete, will have four PhD-level experts in different areas of nanofabrication and nanocharacterization.

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Full job announcement can be found here

Commercializing your Research

Sometimes I stay awake in the night thinking – how soon will the results of my work become useful for humanity? Well, better get up and do something about it! And so a few months ago we have started a new scientific equipment company, based on research breakthroughs in the field of topological quantum matter.

The new company is called ‘Pittsburgh Instruments’ to honor the long-standing tradition of naming something after a city. We currently have three employees, and a distinguished board of advisers though some of the founders of our technology are sadly, no longer with us. The website for the company, along with the Kickstarter page are going online as I write this.

We actually already have a prototype of our first instrument. Please welcome:

Chernnumberometer 1.0 from Pittsburgh Instruments, going on sale December 31 2016

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It is a sleekly designed high tech gadget which can measure a Chern number of anything that fits inside! Just open the door, put your item of choice in.Select Integration Time. Press start. The machine will rotate the object to examine it. Then the digital display will show you the answer. For example, if you put a doughnut inside it will read 0, if you put an orange it will read 1. You can read pretty high numbers if you put in something like this. Give it a try! You can also easily switch a topological invariant that you want to measure from Chern number to a Z2 or a determinant of a scattering matrix for 1D systems. Nevermind that labels say ‘Chicken’ or ‘Popcorn’ – this is an inside joke from the company, we like to be cool like Android developers. For example ‘Defrost’ refers to a very advanced renormalization group-based algorithm.

Our target population are theoretical physicists who have an incessant desire to know things about physical systems that cannot be measured. This compact and elegant Chernnumberometer fits on an office desk, in the coffee area or even at your house! Priced at just $3,999 it also fits on almost any grant. Make sure to mention it in your next proposal!

(Some of the issues we are still working out are dynamic cooling, as certain samples we reported to get very hot. The final release might actually feature a helium compressor bumping the price to $53,999. Also, don’t try to measure Chern numbers of your pets or eggs)

Spin Transistor Explanation

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This gif filmed in Tofino is from 2008 and it explains the ‘injector-detector’ device used to generate and measure spin currents. Charge currents flow to the left, while spin currents flow both ways.

It pertains, for example, to this paper we wrote: http://arxiv.org/abs/1208.3106 (this is an arxiv-only publication!)

 

Introduction to Solid State Physics

Last semester I recorded 23 lectures on Solid State Physics for Undergraduate students. The first 15 lectures are following the wonderful texbook by Steven Simon “Oxford Solid State Basics”, and the last lectures cover superconductivity and advanced topics from Quantum Transport. This class can be a prequel to my Quantum Transport course and I hope it will be useful for students thinking of going into condensed matter research.

Because this is so great for binge watching, I am releasing the whole season at once.

Back to the Future

So there is this great movie that you should totally go see, it is about an eccentric scientist who befriends a simple-minded neighborhood teenager and sends him backwards in time in a car converted into a time machine…

Something like this just happened in our lab. We started out a couple of years ago as a cryogen-free operation. Instead of relying of liquid helium, we used closed-cycle cryostats where helium circulates between a compressor and a cryostat and extracts heat from a vacuum-shielded volume. There are two reasons why cryogen-free systems are great – they save money on (pricey) liquid helium and they are easy to operate at a push of a button.

But in the meantime our generous university set up a helium liquefier, which supplies nearly-free liquid helium to us. And so now we built our first liquid helium setup – a dunker stick! It derives its name from a concept of dunking your specimen into liquid helium in order to reach a low temperature of 4.2 Kelvin, at which helium is stored in liquid form.

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From the technological point of view, it is a step back compared to our cryofree setups. But we can use it for many quick measurements and tests, which is great.

Miro at the Nanoscale

Optical microscopy images of a silicon wafer covered with PMMA and silicon nitride. The structures appeared when silicon nitride was sputtered onto the wafer.

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Rashba Effect at 35

Last year was the 35th anniversary of the seminal paper by Bychkov and Rashba which introduced a spin-orbit coupling which is now known as “the Rashba effect“. It is a beautiful piece of physics that brings a bit of relativity into condensed matter world. Turns out, in an electric field (or under a broken symmetry) electron spins in a solid can behave as if they are in a magnetic field.

Anyhow, 35 years later the Rashba effect lives on and find itself at the frontiers of some of the hottest research of the 21-st century, as you can convince yourself by arxiving it (it is like googling but with arxiv.org).

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So a few months ago Aurelien Manchon approached me and several other folks to be part of a review of what is the face of Rashba effect 35 years later. As with all manuscripts, preparation took forever, so we are celebrating the 35th birthday of Rashba effect one year later. But finally the paper it out there and we are hoping it can serve those who want to know how Rashba spin-orbit physics beats along with spintronics, quantum computing, topological physics and cold atomic research.

I learned a lot about spin-orbit interaction myself from working on this review, I also learned the difference between stirring and steering, as in ‘steering wheel’ not ‘stirring wheel’ (thank you, anonymous referee!).

Helium Liquefier

Our University has sacrificed a parking lot to realize this project:

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It is an expansion to the machine shop which among other things now hosts this helium liquefier:

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Our lab is now connected to the helium recovery system, and we are building our first “wet” cryostat in which liquefied helium is used to cool a sample to 4.2 degrees Kelvin (-269 degrees centigrade). We are also now officially shopping for a used wet dilution refrigerator.

Quantum Triangles

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A friend once told me that all that physicists ever measure is either a sine wave or a straight line. Nothing proves him wrong better than this piece of data we obtained by measuring on a semiconductor nanowire device (Ge/Si nanowires). These double-triangles represent a charge stability diagram of a double quantum dot. Charge stability actually happens in between the triangles, where current is zero (blue), and the number of charges on each of the two quantum dots is fixed. We don’t know how many charges are there on each dot but it is few tens. In the triangular regions, charges move because they have enough energy to jump from one quantum dot into the other and out into the lead that takes them to our ammeter. Inside the triangles, we get a glimpse of quantum energy levels, orbital and spin, of the particles trapped in quantum dots – those energy levels are the stripes of the triangles. The axes of the graphs are voltages on remote electrodes located 10 nanometers away from the nanowire, voltages on these electrodes (gates) are used to change the capacitive energy of the quantum dots.

Pittsburgh Nano Jobs

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Our university’s Nanoscience Institute (PINSE) is looking for a Technical Director to run the nanofabrication and characterization facility. The job is part of a major reinvestment effort, and the new Director will play a central role in how the facility will look and operate going forward. We want to attract a truly outstanding candidate, so we are trying to spread the word as far and wide as we can.

The job ad is here: PINSE Technical Director

http://nano.pitt.edu/

Happy 2015!

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Wish you all great discoveries and a lot of fun with science.